Channel measurement is an important basis for a base station to perform scheduling and selecting transmission parameters. Therefore, accuracy of the measurement result directly affects system performance.
At present, the system bandwidth is the measurement object in various wireless communication systems. For example, in an LTE (Long Time Evolution, long time evolution) system, the PMI (Pre-coding Matrix Indicator, pre-coding matrix indicator) and CQI (Channel Quality Indicator, channel quality indicator) are two important parts of CSI (Channel State Information, channel state information). During channel measurement, a terminal measures the channel state at the entire system bandwidth, and feeds back CSI information obtained through measurement to a base station. In some scenarios, for example, in the low load scenario, only a small portion of the system bandwidth is activated and data is transmitted by using the activated bandwidth. Therefore, the measurement of the channel state within the entire system bandwidth is not accurate. Meanwhile, when a sub-band is measured at the entire system bandwidth, the terminal feeds back a large amount of CSI of the sub-band within the non-activated bandwidth. This results in invalid feedback and wastes the uplink signaling resources.
In addition, an operator has some bandwidth, for example, 7 M. The bandwidth is not standard bandwidth that is supported by the LTE and LTE-A (LTE Advanced, LTE advanced). A common solution for supporting such non-standard bandwidth is to divide the bandwidth into two component carriers of standard bandwidth, for example, 5 M and 3 M, and use a CA (Carrier Aggregation, carrier aggregation) technology. The actual bandwidth is 7 M, not 5 M+3 M, and the remaining 1 M bandwidth is not used to transmit data. Currently, the system bandwidth supported by the terminal is the standard bandwidth, and the system bandwidth is the measurement range. Therefore, the terminal can only measure the channel state information of the 5 M+3 M bandwidth. In this case, the interference produced at the 5 M+3 M−7 M bandwidth affects the accuracy of the channel measurement. In addition, when the sub-band is measured within the 5 M+3 M bandwidth, the terminal feeds back the CSI of the sub-band at the 5 M+3 M−7 M bandwidth to the base station as measurement results. This results in invalid feedback and wastes the uplink signaling resources.
In conclusion, in the prior art, the system bandwidth is taken as the measurement object, which may cause inaccuracy of the measurement and invalid feedback in some scenarios, for example, low load and CA.